-LRB- CNN -RRB- -- The U.S. relationship with President Hosni Mubarak 's Egypt is full of contradictions and tensions , according to recently published U.S. diplomatic cables , but is also underpinned by similar basic interests in a rough and unpredictable part of the world .

A CNN analysis of secret and confidential cables published by WikiLeaks and its media partners reveals U.S. frustration with Mubarak 's lack of succession planning , concerns over stuttering economic reform and private criticism of the Mubarak government 's hard line toward domestic opponents .

But the cables also show that Washington sees Egypt as an important and -- until now -- stable ally on issues , including Iran 's nuclear program , promoting negotiations between Israel and the Palestinian Authority and making life difficult for Hamas in Gaza .

And above all , Egypt is regarded as a moderate bulwark against Iranian-sponsored Islamist fundamentalism .

The cables show that Mubarak has taken a persistently hard line toward Iran , telling U.S. diplomats in 2008 that he had warned Tehran `` not to provoke the Americans '' on the nuclear issue and insisting Egypt could never accept a nuclear-armed Iran .

Mubarak has also repeatedly warned of Iran 's influence with Hamas in Gaza and Hezbollah in Lebanon , and in a cable from February last year , was quoted as describing `` Tehran 's hand moving with ease throughout the region , from the Gulf to Morocco . ''

A 2009 cable noted that with `` the discovery of a Hezbollah cell in Egypt , the Egyptians appear more willing to confront the Iranian surrogates and to work closely with Israel . '' To that end , the cables describe the Mubarak government as a helpful partner in stopping smuggling into Gaza from Egypt . A cable from 2008 quoted a senior Egyptian military figure as stating that Egypt had spent approximately $ 40 million to purchase the steel for an underground wall on the Gaza border , `` and Egypt was paying the cost of this wall in terms of public opinion both within Egypt and the region . ''

There is no guarantee that any `` successor '' to the Mubarak government would take such a hard line with Hamas .

For the U.S. , the alliance between Egypt and Saudi Arabia has also been an important counterweight to growing Iranian influence on the `` Arab street '' and among states such as Syria and Qatar .

Egyptian officials , from Mubarak down , have also repeatedly impressed upon visiting Americans -- military , diplomatic and Congressional -- that it alone among Arab states can play a mediating role between Israel and the Palestinians . -LSB- Egypt signed a peace treaty with Israel in 1979 , and Mubarak has resisted popular opposition to it . -RSB-

Ahead of Mubarak 's visit to Washington in May 2009 , Ambassador Margaret Scobey wrote from Cairo that `` the Egyptians want the visit to demonstrate that Egypt remains America 's indispensable `` Arab ally . ''

Scobey continued that Mubarak was `` a tried and true realist , innately cautious and conservative , and has little time for idealistic goals . ''

He viewed himself as `` someone who is tough but fair , who ensures the basic needs of his people . ''

At the same time , the Mubarak government has been very sensitive to any perceived slight from Washington . It has complained about cuts in U.S. economic aid and a stagnant level of military aid `` because it shows our diminished view of the value of our relationship '' according to one cable .

On pressure to improve human rights , according to one cable from Scobey in 2009 , `` Mubarak takes this issue personally , and it makes him seethe when we raise it , particularly in public . ''

In a later cable , she said that Mubarak `` harkens back to the Shah of Iran : the U.S. encouraged him to accept reforms , only to watch the country fall into the hands of revolutionary religious extremists . ''

The Egyptian president relied on his interior minister and intelligence service to `` keep the domestic beasts at bay , and Mubarak is not one to lose sleep over their tactics . ''

The U.S. cables display frustration with Mubarak 's reluctance to address human rights issues , with one in 2008 saying : `` While Egypt has made some limited gains over the last several years , such as on freedom of the press , progress overall has been slow . ''

In a later cable , Scobey suggested the new U.S. Secretary of State , Hillary Clinton `` may wish to lay down a marker for a future discussion on democratization and human rights concerns . '' But given Mubarak 's sensitivities , the U.S. has trodden carefully in pressing the Egyptian government on human rights . A cable from 2009 said the United States now avoided `` the public confrontations that had become routine over the past several years '' over human rights .

Over the past five years , the cables reveal a growing unease with the lack of a succession plan , and apprehension about the prospect of Mubarak 's younger son , Gamal , taking over from his father . As far back as April 2006 , one cable observed that Mubarak 's wife , Suzanne , was their son 's `` most ardent booster '' but added : `` The possibility that Gamal might succeed his father remains deeply unpopular on the street . ''

It adds that `` unlike his father , -LRB- Gamal -RRB- can not take the military 's support for granted , '' having never served as an officer . But the same cable laments the lack of obvious contenders to succeed the aging Mubarak -- a situation that appears to hold today .

Scobey wrote in apparent frustration two years ago that Mubarak `` seems to be trusting to God and the ubiquitous military and civilian security services to ensure an orderly transition . ''

Recent events may have eroded that confidence , but one cable in 2007 pointed out that Egypt 's internal security apparatus , `` an estimated 1.4 million strong , is at least twice the size it was under Sadat ... and makes any kind of violent change of leader unlikely . ''

That perspective is now being challenged -- and the role of the military may be critical in deciding the outcome . A cable from 2008 cites Egyptian experts as describing a `` disgruntled mid-level officer corps '' with military salaries falling far behind the civilian sector and the top brass averse to Gamal succeeding his father .

Egyptian commentators also noted that many officers were frustrated that loyalty to the regime trumped competence , and that the best military talent was sidelined in case it should pose a threat to the government . Even so , one cable concludes : `` The military still remains a potent political and economic force . ''

After discussing whether the military might step in to prevent Mubarak from passing the baton to his son , the cable concludes : `` In a messier succession scenario , however , it becomes more difficult to predict the military 's actions . ''

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A CNN analysis of secret cables published by WikiLeaks reveals U.S. frustration

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U.S. has concerns over economic reform , Mubarak 's lack of succession planning

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Cables also reveal Washington sees Egypt as an important and -- until now -- stable ally